短花针茅荒漠草原物种间关系的多度不对称性对载畜率的响应

目前物种的相对多度与种间关系的内部联系如何影响物种共存仍不清楚。为探讨植物群落物种间关系强度的多度不对称性及其对载畜率的响应，本研究以内蒙古短花针茅(Stipa breviflora)荒漠草原植物群落为对象，分析了对照、轻度、中度及重度放牧下群落物种的多度及其频率。结果表明：随载畜率的增大，物种数呈现出降低的趋势。不同载畜率下同分布指数CO均存在明显的多度依赖性；常见种(如短花针茅、无芒隐子草(Cleistogenes songorica)及刺穗藜(Chenopodum aristatum))对其他物种的作用强度普遍较强。不同载畜率下短花针茅对无芒隐子草及刺穗藜的作用强度均高于其二者对短花针茅的强度，表现出种间强度的不对称性。此外，放牧使得短花针茅对无芒隐子草的作用强度呈现出增大的趋势，使得无芒隐子草对短花针茅的作用强度呈现出降低的趋势。因此，物种间存在多度的不对称性，而放牧进一步造成其物种间作用强度的变化。

Responses of Abundance-asymmetric of Interspecific Interaction to Stocking Rates in the Stipa breviflora Desert Steppe

The relationship between the relative abundance of species and its interspecific relationship affecting the coexistence of species is unclear. We conducted a grazing experiment to test abundance-asymmetric of interspecific interaction in the plant communities and its responses to different stocking rates including the control,light grazing,moderate grazing and heavy grazing in the Stipa breviflora desert steppe in Inner Mongolia. Taking the plant communities of S. breviflora desert steppe as the research objects,the abundance and frequency of all species in the communities under control,light grazing,moderate grazing and heavy grazing were analyzed. The results showed the numbers of species in the steppe had a decreasing trend with increasing stocking rates. The codistribution index of species pairs had a significant dependence on its abundance under all different stocking rates,and common species (e.g.,S. breviflora,C. songorica and C. aristatum) had a generally stronger effect on the abundance of other species. The interaction intensity of S. breviflora on C. songorica and C. aristatum was higher than that of C. songorica and C. aristatum on S. breviflora under all different stocking rates,showing the existence of abundance-asymmetric of interspecific interaction. Besides,grazing increased the interaction intensity of S. breviflora on C. songorica,while decreased the interaction intensity of C. songorica on S. breviflora. As a summary,there was an abundance-asymmetric of interspecific interaction among species,and the livestock grazing further imposed a change on the intensity of interspecific interaction.